HTTP is all about sending and receiving knowledge over the community. Initially it was solely utilized to switch HTML paperwork, however these days we use HTTP to switch CSS, JavaScript, JSON and plenty of different knowledge sorts. In response to the requirements, the Content material-Sort and Content material-Size headers can be utilized to have a greater understanding in regards to the knowledge contained in the physique of the HTTP request.
Trendy net servers can routinely ship again these headers based mostly on the thing you come in a request handler operate. That is the case with Hummingbird, it has built-in encoding and decoding assist, which makes the info transformation course of actually easy.
For instance if we setup the next route handler and name the whats up endpoint utilizing cURL with the -i flag, the output will include a bit extra details about the response. ℹ️
router.get("whats up") { _ in "whats up" }
There are some fundamental headers within the response, the content-type header incorporates the kind of the physique, which is at present a plain textual content with an UTF-8 encoded string, since we have returned a String kind utilizing our Swift code. The content-length is 5, as a result of the character depend of whats up is 5.
There are another headers, however ignore these, the fascinating half for us is the content-type header, and the way it’s injected into the response. Each Hummingbird software has an encoder and a decoder property. The default values for these are NullEncoder and NullDecoder. The encoders can magically add the correct content material kind header to the response and encode some object right into a HTTP response knowledge. Not every little thing is response encodable and decodable by default, however you may encode String objects in Hummingbird by default. 👍
Encoding and decoding JSON objects
Most of the server-side Swift methods are used to create JSON-based RESTful API backends for cellular frontends. Hummingbird may help you with this, because it has built-in encoding and decoding assist for JSON objects via the Codable protocol.
First it’s important to import the HummingbirdFoundation library, since it’s a standalone helper instrument constructed across the Basis framework, and that bundle incorporates the Codable kind extensions. Subsequent it’s important to setup the encoder and decoder utilizing a JSONEncoder and JSONDecoder occasion. After this, you may simply rework incoming HTTP physique objects into Swift knowledge buildings and return with them as nicely. Let me present you a fast instance. ⤵️
import Hummingbird
import HummingbirdFoundation
struct Foo: Codable {
let bar: String
let baz: Int
}
extension Foo: HBResponseCodable {}
extension HBApplication {
func configure(_ args: AppArguments) throws {
decoder = JSONDecoder()
encoder = JSONEncoder()
router.submit("foo") { req async throws -> Foo in
guard let foo = strive? req.decode(as: Foo.self) else {
throw HBHTTPError(.badRequest, message: "Invalid request physique.")
}
return foo
}
}
}As you may see the kind of the returned content material is now correctly set to software/json and the size can be offered by default. We have been additionally capable of decode the Foo object from the request physique and routinely encode the thing after we returned with it.
Codable routing works like magic and these days it is a fairly customary strategy if it involves server-side Swift frameworks. Enjoyable truth: this strategy was initially ‘invented’ for Swift by the builders of the Kitura framework. Thanks. 🙏
The HBResponseCodable and the HBResponseEncodable protocols are the essential constructing blocks and the HBRequestDecoder and the HBResponseEncoder are answerable for this magic. They make it doable to decode a Decodable object from a HBRequest and encode issues right into a HBResponse object and likewise present extra headers. If you need to know extra, I extremely suggest to check out the JSONCoding.swift file contained in the framework. 😉
Encoding and decoding HTML kinds
I do not wish to get an excessive amount of into the main points of constructing kinds utilizing HTML code, by the best way there’s a higher manner utilizing SwiftHtml, however I might wish to focus extra on the underlying knowledge switch mechanism and the enctype attribute. There are 3 doable, however solely two helpful values of the encoding kind:
- software/x-www-form-urlencoded
- multipart/form-data
URL encoding and decoding is supported out of the field when utilizing HummingbirdFoundation, it is a easy wrapper across the URL encoding mechanism to simply assist knowledge transformation.
decoder = URLEncodedFormDecoder()
encoder = URLEncodedFormEncoder()
In order that’s one option to course of a URL encoded type, the opposite model is predicated on the multipart strategy, which has no built-in assist in Hummingbird, however you should utilize the multipart-kit library from the Vapor framework to course of such kinds. You could find a working instance right here. I even have an article about the best way to add information utilizing multipart type knowledge requests. So there are many assets on the market, that is why I will not embrace an instance on this article. 😅
Header based mostly encoding and decoding
First we’ve got to implement a customized request decoder and a response encoder. Within the decoder, we will verify the Content material-Sort header for a given request and decode the HTTP physique based mostly on that. The encoder will do the very same factor, however the response physique output goes to rely on the Settle for header subject. Here is how one can implement it:
struct AppDecoder: HBRequestDecoder {
func decode<T>(
_ kind: T.Sort,
from req: HBRequest
) throws -> T the place T: Decodable {
swap req.headers["content-type"].first {
case "software/json", "software/json; charset=utf-8":
return strive JSONDecoder().decode(kind, from: req)
case "software/x-www-form-urlencoded":
return strive URLEncodedFormDecoder().decode(kind, from: req)
default:
throw HBHTTPError(.badRequest)
}
}
}
struct AppEncoder: HBResponseEncoder {
func encode<T>(
_ worth: T,
from req: HBRequest
) throws -> HBResponse the place T: Encodable {
swap req.headers["accept"].first {
case "software/json":
return strive JSONEncoder().encode(worth, from: req)
case "software/x-www-form-urlencoded":
return strive URLEncodedFormEncoder().encode(worth, from: req)
default:
throw HBHTTPError(.badRequest)
}
}
}Now in the event you change the configuration and use the AppEncoder & AppDecoder it is best to be capable of reply based mostly on the Settle for header and course of the enter based mostly on the Content material-Sort header.
import Hummingbird
import HummingbirdFoundation
struct Foo: Codable {
let bar: String
let baz: Int
}
extension Foo: HBResponseEncodable {}
extension Foo: HBResponseCodable {}
extension HBApplication {
func configure(_ args: AppArguments) throws {
decoder = AppDecoder()
encoder = AppEncoder()
router.submit("foo") { req async throws -> Foo in
guard let foo = strive? req.decode(as: Foo.self) else {
throw HBHTTPError(.badRequest, message: "Invalid request physique.")
}
return foo
}
}
}Be happy to mess around with some cURL snippets… 👾
# ought to return JSON encoded knowledge
curl -i -X POST http://localhost:8080/foo
-H "Content material-Sort: software/x-www-form-urlencoded"
-H "Settle for: software/json"
--data-raw 'bar=bar&baz=42'
# ought to return URL encoded knowledge
curl -i -X POST http://localhost:8080/foo
-H "Content material-Sort: software/json"
-H "Settle for: software/x-www-form-urlencoded"
--data-raw '{"bar": "bar", "baz": 42}'
# ought to return with a 400 standing code
curl -i -X POST http://localhost:8080/foo
-H "Content material-Sort: software/json"
-H "Settle for: multipart/form-data"
--data-raw '{"bar": "bar", "baz": 42}'
So, based mostly on this text it is best to be capable of implement assist to much more content material sorts by merely extending the app encoder and decoder. After all you might need to import some extra bundle dependencies, however that is positive.
Uncooked requests and responses
Yet one more little factor, earlier than I finish this text: you may entry the uncooked request physique knowledge and ship again a uncooked response utilizing the HBResponse object like this:
router.submit("foo") { req async throws -> HBResponse in
if let buffer = req.physique.buffer {
let rawInputData = buffer.getData(
at: 0,
size: buffer.readableBytes
)
print(rawInputData)
}
if let sequence = req.physique.stream?.sequence {
for strive await chunk in sequence {
print(chunk)
}
}
guard let knowledge = "whats up".knowledge(utilizing: .utf8) else {
throw HBHTTPError(.internalServerError)
}
return .init(
standing: .okay,
headers: .init(),
physique: .byteBuffer(.init(knowledge: knowledge))
)
}For smaller requests, you should utilize the req.physique.buffer property and switch it right into a Information kind if wanted. Hummingbird has nice assist for the brand new Swift Concurreny API, so you should utilize the sequence on the physique stream in the event you want chunked reads. Now just one query left:
What sorts ought to I assist?
The reply is easy: it relies upon. Like actually. These days I began to ditch multipart encoding and I choose to speak with my API utilizing REST (JSON) and add information as uncooked HTTP physique. I by no means actually needed to assist URL encoding, as a result of in the event you submit HTML kinds, you will finally face the necessity of file add and that will not work with URL encoded kinds, however solely with multipart.
In conclusion I might say that the excellent news is that we’ve got loads of alternatives and if you wish to present assist for many of those sorts you do not have to reinvent the wheel in any respect. The multipart-kit library is constructed into Vapor 4, however that is one of many causes I began to love Hummingbird a bit extra, as a result of I can solely embrace what I really want. Anyway, competitors is an efficient factor to have on this case, as a result of hopefully each frameworks will evolve for good… 🙃
